Method of Increasing Deposition Rate of Silicon Dioxide on a Catalyst

ABSTRACT

Methods for forming dielectric layers, and structures and devices resulting from such methods, and systems that incorporate the devices are provided. The invention provides an aluminum oxide/silicon oxide laminate film formed by sequentially exposing a substrate to an organoaluminum catalyst to form a monolayer over the surface, remote plasmas of oxygen and nitrogen to convert the organoaluminum layer to a porous aluminum oxide layer, and a silanol precursor to form a thick layer of silicon dioxide over the porous oxide layer. The process provides an increased rate of deposition of the silicon dioxide, with each cycle producing a thick layer of silicon dioxide of about  120 Å  over the layer of porous aluminum oxide.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. Ser. No. 10/930,149, filedAug. 31, 2004, now U.S. Pat. No. 8,158,488.

FIELD OF THE INVENTION

The invention relates generally to semiconductor processing methods offorming dielectric fill materials, and more particularly to methods offorming silicon dioxide layers on substrates using a catalyst.

BACKGROUND OF THE INVENTION

Insulative materials are widely used in semiconductor fabricationmethods for forming structures to electrically isolate the variousactive components formed in integrated circuits. Devices that extendinto a semiconductive substrate can be electrically isolated byinsulative materials formed within the substrate between the components,for example, trench isolation regions. In such a technique, trenches areetched into a silicon substrate, usually by anisotropic etching, and thetrenches are subsequently filled by the deposition of an oxide such assilicon dioxide (SiO₂).

Due to the reduction in component size, microelectronic devices nowrequire processing methods for forming nanosized components andaccompanying silicon dioxide films. Such films have been achieved usingatomic layer deposition (ALD) to control the growth of the film.

ALD processes proceed by chemisorption of a monolayer of reactiveprecursor molecules at the surface of the substrate. A series ofreactive precursors are then alternately pulsed into a depositionchamber, separated by an inert gas purge. Each pulse of a precursorresults in a new atomic layer over the previously deposited layers. Thecycle is repeated until a desired film thickness is achieved.

However, the rate of deposition of silicon dioxide to fill a trench orother opening using an ALD process is less than desirable.

SUMMARY OF THE INVENTION

The present invention provides methods of forming insulative materials,and semiconductor devices and systems incorporating the insulativematerials. In particular, the invention provides methods for forming athick dielectric film utilizing a catalyst layer of an organoaluminumcompound.

To form the dielectric layer according to the invention, alternatingthin layers of aluminum oxide and thick layers of silicon dioxide areformed by pulsing an organoaluminum precursor into a deposition chamberfor a set period of time to deposit a monolayer of the organoaluminum(catalyst) material over the substrate, purging the unreactedorganoaluminum precursor material from the chamber, pulsing an activeoxygen and active nitrogen source into the chamber for a set period oftime to oxidize and convert the organoaluminum monolayer to a porousaluminum oxide layer, and then pulsing a silanol precursor into thechamber for a set period of time to deposit the silanol material ontothe porous aluminum oxide layer to grow a thick layer of silicon oxide.

In one embodiment of the method of the invention, trimethylaluminum(TMA) catalyst or triethyl(tri-sec-butoxy)dialuminum (TETBAL) catalystis deposited as a monolayer over the substrate, the unreacted catalystis purged from the deposition chamber, the catalyst layer on thesubstrate is exposed to a remote plasma oxygen source gas (e.g., O₃) anda small amount of a remote plasma nitrogen source gas (e.g., N₂),preferably containing less than about 1% nitrogen, to convert the layerto a porous aluminum oxide layer, and a silanol precursor gas such astris(tert-butoxy)silanol (TBOS) is deposited onto the porous aluminumoxide layer to form a thick silicon dioxide (SiO₂) layer. The unreactedsilanol material can then be purged from the deposition chamber, and thecycle or sequence of depositing a monolayer of the TMA or TETBALcatalyst, purging the chamber, exposing the monolayer of the catalyst tothe remote oxygen/nitrogen (O₃/N₂) plasma to form the porous aluminumoxide layer, and depositing the silanol precursor onto the aluminumoxide layer, and then purging the chamber, can be repeated to formadditional layers and to provide a film having the desired thickness.The process forms a laminate structure composed of alternating thinlayers (monolayers of about 3-10 angstroms) of aluminum oxide and thicklayers of SiO₂. The process achieves an about 12% increase in thesilicon dioxide deposition or growth rate per cycle compared toprocesses that do not utilize an organoaluminum catalyst layer and theoxygen/nitrogen processing step prior to depositing the silanolprecursor, resulting in the deposition of an about 100-300 Å thick layerof silicon dioxide.

In other aspects, the invention provides integrated circuits that caninclude an array of memory cells and internal circuitry, electronicsystems that can comprise a microprocessor and a memory device coupledto the microprocessor, and electronic systems that include a processorand an integrated circuit (e.g., a memory circuit such as a DRAM memorycircuit) in communication with the processor, which incorporate anisolation structure made according to the invention of alternatinglayers of a porous aluminum oxide monolayer and an about 100-300 Å thicklayer of silicon dioxide.

The invention is useful in forming silicon dioxide layers over featuresthat have flat surfaces to features such as contact openings andtrenches having a high aspect ratio of up to about 20-30:1 and higher,providing good step coverage over the sidewalls and base of the featureat a low deposition temperature. The higher deposition rate of thesilicon dioxide results in a higher throughput and increased productionoutput. The invention provides a useful process for forming nanofilmsthat are useful in applications such as fiber electronics, among others.In addition, the porous aluminum oxide (Al₂O₃) layer has a lower k valuethan dense Al₂O₃, which is useful in IMD applications where lowerparasitic capacitance is desirable.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings, which are forillustrative purposes only. Throughout the following views, thereference numerals will be used in the drawings, and the same referencenumerals will be used throughout the several views and in thedescription to indicate same or like parts.

FIG. 1 is a diagrammatic, cross-sectional view of a semiconductorconstruction at a preliminary processing stage of an exemplaryapplication of the present invention.

FIGS. 2-6 are views of the FIG. 1 wafer fragment at sequentialprocessing steps subsequent to that of FIG. 1 according to an embodimentof the method of the invention.

FIG. 7 is a block diagram of a circuit module according to an embodimentof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention will be described generally with reference to the drawingsfor the purpose of illustrating the present preferred embodiments onlyand not for purposes of limiting the same. The figures illustrateprocessing steps for use in the fabrication of semiconductor devices inaccordance with the present invention. It should be readily apparentthat the processing steps are only a portion of the entire fabricationprocess.

In the context of the current application, the term “semiconductorsubstrate” or “semiconductive substrate” or “semiconductive waferfragment” or “wafer fragment” or “wafer” will be understood to mean anyconstruction comprising semiconductor material, including but notlimited to bulk semiconductive materials such as a semiconductor wafer(either alone or in assemblies comprising other materials thereon), andsemiconductive material layers (either alone or in assemblies comprisingother materials). The term “substrate” refers to any supportingstructure including, but not limited to, the semiconductive substrates,wafer fragments or wafers described above.

FIGS. 1-6 illustrate steps in an embodiment of a method of the inventionfor fabricating an insulative layer for a trench isolation feature in asemiconductive substrate. Other semiconductor structures than isolationtrenches can also benefit from the insulative layer of the invention.Thus, the method is not limited to the specific illustrated embodimentand has broad application to a variety of applications in IC fabricationfor shallow trench isolations (STI), gate spacers, spacers betweenwordlines, buried digit line spacers, among others.

Referring to FIG. 1, an exemplary semiconductor wafer fragment at apreliminary processing step is indicated generally with referencenumeral 10. The wafer fragment 10 comprises a substrate 12, which cancomprise an unprocessed semiconductor wafer or other substrate, thewafer with various process layers formed thereon including one or moresemiconductor layers or other formations, and active or operableportions of semiconductor devices such as transistors, capacitors,electrodes, insulators, or any of a variety of components commonlyutilized in semiconductor structures. The substrate 12 can comprise asemiconductive material such as monocrystalline silicon, polycrystallinesilicon, germanium, or gallium arsenide, or epitaxial layers of siliconsupport by a base semiconductor foundation, for example, or aninsulating layer if silicon-on-insulator (S—O—I) or a similar technologyis used. The process of the present invention has broad application to awide variety of substrates 12. In the illustrated example, the substrate12 comprises a semiconductive material such as monocrystalline siliconthat is lightly doped with a conductivity enhancing material.

As shown, a trench 14 has been formed into the semiconductive substrate12. The trench can be formed, for example, by forming a patterned layerof photoresist and etching the substrate to form the trench 14,according to known techniques. The trench 14 includes sidewalls 16 and abottom (base) 18. The wafer 10 further includes a pad oxide layer 20overlying the substrate 12, and an overlying silicon nitride layer 22.

An oxide isolation structure is formed in the trench 14 by formingalternating layers of porous aluminum oxide and silicon dioxide.

Referring to FIG. 2, a monolayer 24 of an organoaluminum (catalyst)material (e.g., about 3-10 Å) is deposited over the substrate and alongthe sidewalls 16 and bottom 18 within the trench 14. The organoaluminumlayer 24 can be formed by atomic layer deposition (ALD) processing in adeposition chamber, which includes exposing the substrate to a gaseousorganoaluminum precursor to form a monolayer onto the surface withorganic groups (e.g., methyl groups) pending from the chemisorbedaluminum.

The organoaluminum precursor may be any suitable organic compound thatwill allow the aluminum to deposit from the gas phase onto a substrateunder ALD conditions and chemisorb to the surface of the substrate withorganic groups (e.g., methyl groups) available for oxidation. Exemplaryorganoaluminum precursors include aluminum alkyls such astrimethylaluminum (TMA), triethylaluminum, triisobutylaluminum, and thelike; alkylaluminum alkoxides such as triethyl(tri-sec-butoxy)dialuminum(TETBAL), and the like; and aluminum amides such as Al₂(NEt₂)₆,Al₂(NEtMe)₆, Al₂(NMe₂)₆, and the like.

A standard ALD process can be used to deposit the organoaluminumcompound, which generally employs precursor sources that are deliveredfrom a vaporization chamber to a reactor chamber where the depositiononto the target substrate occurs. The organoaluminum precursor can bevaporized by known methods. For example, a liquid form of theorganoaluminum precursor can be placed in a bubbler and heated (ifnecessary) to its vaporization temperature, and the vaporized precursormaterial can then be either directly introduced into the reactionchamber, or transported by a carrier gas (e.g., Ar, He, etc.) passingover the bubbler or through the liquid precursor. The precursor can alsobe contained in a temperature-controlled vessel such as an ampoulehaving an outlet to deliver the vaporized precursor to the depositionchamber. For example, trimethylaluminum (TMA) can be held in an ampouleat about room temperature (about 20° C.), and pulses of the TMA vaporcan be delivered through a valve into the deposition chamber.

Generally, the process parameters include a reaction chamber temperatureof about 180-350° C., preferably about 200-320° C., and typically about230° C., and a chamber pressure of about 0.5-10 Torr, preferably about 1Torr. The cycle duration (pulsing) of the organoaluminum precursor(e.g., trimethylaluminum) is typically about 1-5 seconds, preferablyabout 1 second, to deposit about a monolayer 24 of the organoaluminumcompound onto the surface of the substrate.

The unreacted organoaluminum precursor is then purged from the surfaceof the substrate and the deposition chamber. The purging can beconducted with an inert gas such as nitrogen (N₂), argon (Ar), helium(He), neon (Ne), Krypton (Kr), xenon (Xe), and the like, at a flow rateof about 500-1,000 sccm for about 1-30 seconds, preferably about 10seconds.

As depicted in FIG. 3, the organoaluminum monolayer 24 is then exposedto an active oxygen source and an active nitrogen source 26 to produce aroughened and porous aluminum oxide (Al₂O₃) layer 28 on the substrate.Preferably, the organoaluminum monolayer 24 is exposed to a remoteoxygen plasma and a small amount of a remote nitrogen plasma. Exemplaryoxygen and nitrogen sources include ozone (O₃), hydrogen peroxide (H₂O₂)vapor, water (H₂O) vapor, oxygen (O₂), nitrogen (N₂), nitrous oxide(N₂O), nitrogen dioxide (NO₂), and nitric oxide (NO), being ozone (O₃)and nitrogen (N₂) in the illustrated example.

It has been found that the presence of nitrogen in the oxygen processgas results in the desired porosity in the oxide layer 28. A preferredconcentration of a remote plasma nitrogen is about 0.01-90% by volume,based on the total volume of remote plasma oxygen and remote plasmanitrogen, preferably about 0.1-10% by volume, preferably about 0.1-3% byvolume, and more preferably about 0.01-1% by volume.

As an example, the oxygen/nitrogen treatment process can be conducted byremote microwave plasma using a gas mixture of ozone (O₃) and nitrogen(N₂), along with a carrier gas such as argon or helium, with an ozoneflow of about 500 sccm to about 1 liter per minute, preferably about 750sccm/minute, to provide a gas mixture of about 12-16 wt-% ozone andabout 0.5-1 wt-% nitrogen, at a reaction chamber temperature of about180-350° C., preferably about 200-320° C., and typically about 230° C.,a chamber pressure of about 0.5-10 Ton, preferably about 1 Torr, and anRF power of about 4000 W at a frequency of about 13.5 mHz. The cycleduration (pulsing) of the remote plasma oxygen/nitrogen process can beabout 6-10 seconds, preferably about 8 seconds. The resulting aluminumoxide layer 28 is typically about 1-1.5 Å thick, with an about 50%porosity.

Referring now to FIG. 4, the aluminum oxide layer 28 is then exposed toa silanol precursor 30 to form a thick silicon oxide layer 32. Exemplarysilanols include alkoxysilanols, alkoxyalkylsilanols, alkoxysilanediols,and the like, including tris(alkoxy)silanol compounds such astris(tert-butoxy)silanol (TBOS) and tris(tert-pentyloxy)silanol, andbis(tert-alkoxy)silanediol.

The silanol precursor can be pulsed into the deposition chamber in aninert carrier gas (e.g., N₂, He, Ar, etc.) at a silanol flow rate ofabout 100-500 sccm per minute, typically about 300 sccm per minute, areaction chamber temperature of about 180-350° C., preferably about200-320° C., and typically about 230° C., and a chamber pressure ofabout 0.5-10 Torr, preferably about 1 Torr. The silanol precursor can bedelivered into the reaction chamber by known methods, for example, byvaporizing the silanol in an ampoule or bubbler at 70-100° C., typicallyabout 80° C., and introducing the vaporized silanol in combination witha carrier gas into the chamber. The cycle duration (pulsing) of thesilanol precursor is about 1-60 seconds, preferably about 20 seconds.

The process results in a high deposition (growth) rate of the silicondioxide of about 12% compared to a typical ALD process and processesthat do not treat the organoaluminum layer 24 with an activeoxygen/nitrogen source(s) (e.g., the remote oxygen/remote nitrogenplasma treatment) to form the porous aluminum oxide layer 28 prior todepositing the silanol precursor 30 onto the substrate, resulting in athick layer 32 of silicon dioxide of about 100-300 Å per cycle. Processconditions such as the reaction temperature, pressure, and silanol flowrate, can be optimized by the artisan to vary the thickness of thesilicon dioxide layer 32.

After the formation of the silicon dioxide layer 32, the unreactedsilanol precursor 30 is then purged from the surface of the substrateand the deposition chamber. The purging can be conducted using an inertgas (e.g., Ar, etc.) at a flow rate of about 500-1,000 sccm for about1-30 seconds, preferably about 10 seconds.

The cycle sequential steps) can then be repeated to form additionallayers of the porous aluminum oxide layer 28 and the silicon dioxidelayer 32, as depicted in FIG. 5, which indicates the completion of threecycles (labeled “1”, “2”, “3”) to fill the opening 14 and form theisolation structure 34. The resulting structure is a laminate ofalternating thin layers of porous aluminum oxide 28 and thick layers ofsilicon dioxide (SiO₂) 32.

As depicted in FIG. 6, further processing can be conducted, includingstripping off excess of the oxide fill material formed above the surfaceof the substrate, for example, using a known chemical mechanicalpolishing (CMP) technique, or other technique such as wet etching and/ordry etching.

The process according to the invention, which utilizes the formation ofa porous aluminum oxide layer, advantageously results in a substantiallyincreased growth rate of the silicon dioxide layer, and also offers theadvantage of filling a narrow space, e.g., shallow trench isolation(STI) areas or other opening having a high aspect ratio up to about20-30:1, for example. The process results in a silicon dioxidedeposition rate that is 12% higher than the rate of previously knowndeposition processes, and the formation of a thick layer of silicondioxide (e.g., about 120 Å) with each deposition cycle (e.g., TMAdeposition, silanol deposition).

The resulting isolation structure 34 (e.g., STI) can be used in avariety of applications including, for example, programmable memorydevices, programmable resistor and capacitor devices, optical devices,and sensors, among others.

FIG. 7 is a block diagram of an embodiment of a circuit module 36 inwhich the present invention can be incorporated. Such modules, devicesand systems (e.g., processor systems) incorporating the module aredescribed and illustrated in U.S. Pat. No. 6,437,417 (Gilton) and U.S.Pat. No. 6,465,828 (Agarwal), the disclosures of which are incorporatedby reference herein. In brief, two or more dies may be combined into acircuit module 36 to enhance or extend the functionality of anindividual die. Circuit module 36 may be a combination of diesrepresenting a variety of functions, or a combination of dies containingthe same functionality. One or more dies of the circuit module cancontain circuitry, or integrated circuit devices, that includes at leastone isolation structure in accordance with the embodiments of thepresent invention. The integrated circuit devices can include a memorycell that comprises a structure as discussed in the various embodimentsin accordance with the invention.

Some examples of a circuit module include memory modules, device drivers(on a BIOS or EPROM), power modules, communication modems, processormodules, and application-specific modules, and may include multilayer,multichip modules. Circuit module 36 may be a subcomponent of a varietyof electronic systems, such as a clock, a television, a cell phone, apersonal computer, an automobile, an industrial control system, anaircraft, among others. Circuit module 36 will have a variety of leads38 extending therefrom and coupled to dies 40 providing unilateral orbilateral communication and control.

The circuit module can be incorporated, for example, into an electronicsystem that comprises a user interface, for example, a keyboard,monitor, display, printer, speakers, etc. One or more circuit modulescan comprise a microprocessor that provides information to the userinterface, or is otherwise programmed to carry out particular functionsas is known in the art. The electronic system can comprise, for example,a computer system including a processor and a memory system as asubcomponent, and optionally user interface components, and otherassociated components such as modems, device interface cards, etc.Examples of memory circuits include but are not limited to DRAM (DynamicRandom Access Memory), SRAM (Static Random Access Memory),

Flash memories, a synchronous DRAM such as SGRAM (Synchronous GraphicsRandom Access Memory), SDRAM (Synchronous Dynamic Random Access Memory),SDRAM II, and DDR SDRAM (Double Data Rate SDRAM), as well as Synchlinkor Rambus DRAMs and other emerging memory technologies.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A method for forming a dielectric layer on a substrate, comprising:forming a monolayer of organoaluminum on a substrate; exposing theorganoaluminum monolayer to oxygen and nitrogen gases to form a porousaluminum oxide monolayer; and exposing the porous aluminum oxidemonolayer to a silanol precursor gas to form a layer of silicon dioxideabout 100-300 angstroms thick thereon.
 2. The method of claim 1, whereinthe organoaluminum monolayer is exposed to 0.01-10% by volume nitrogen,based on the total volume of oxygen and nitrogen.
 3. The method of claim1, wherein the organoaluminum monolayer is exposed to 12-16 wt-% ozonegas and 0.5-1 wt-% nitrogen gas.
 4. The method of claim 1, wherein theoxygen gas is selected from the group consisting of ozone, hydrogenperoxide vapor, water vapor and oxygen.
 5. The method of claim 1,wherein the nitrogen gas is selected from the group consisting ofnitrogen, nitrous oxide, nitrogen dioxide and nitric oxide.
 6. Themethod of claim 1, wherein the organoaluminum monolayer is exposed toozone and nitrogen.
 7. The method of claim 1, wherein the organoaluminummonolayer is exposed to a plasma oxygen gas and a plasma nitrogen gas.8. The method of claim 1, wherein forming the organoaluminum monolayercomprises exposing the substrate to a gaseous organoaluminum precursor.9. The method of claim 8, wherein the gaseous organoaluminum precursoris selected from the group consisting of aluminum alkyls, alkylaluminumalkoxides and aluminum amides.
 10. The method of claim 8, wherein thegaseous organoaluminum precursor comprises an aluminum alkyl selectedfrom the group consisting of trimethylaluminum, triethylaluminum, andtriisobutylaluminum.
 11. The method of claim 8, further comprisingpurging excess gaseous organoaluminum precursor from a reaction chambercontaining the substrate.
 12. The method of claim 1, wherein forming theorganoaluminum monolayer comprises depositing an organoaluminumprecursor gas under atomic layer deposition conditions.
 13. The methodof claim 12, wherein forming the organoaluminum monolayer comprisesexposing the substrate to the organoaluminum precursor gas for a timeperiod of 1-5 seconds.
 14. The method of claim 1, wherein exposing theorganoaluminum monolayer to the oxygen and nitrogen gases is for a timeperiod of 6-10 seconds.
 15. The method of claim 1, wherein exposing theporous aluminum oxide monolayer to a silanol precursor gas is for a timeperiod of 1-60 seconds.
 16. The method of claim 1, wherein the silanolprecursor gas is selected from the group consisting of alkoxysilanols,alkoxyalkylsilanols and alkoxysilanediols.
 17. A method for forming adielectric layer on a substrate, comprising: depositing anorganoaluminum precursor gas on a substrate by atomic layer depositionto form a monolayer of organoaluminum; exposing the organoaluminummonolayer to oxygen and nitrogen gases to form a porous aluminum oxidemonolayer; and exposing the porous aluminum oxide monolayer to a silanolprecursor gas to form a layer of silicon dioxide about 100-300 angstromsthick thereon.
 18. The method of claim 17, further comprising removingnon-absorbed organoaluminum precursor gas from a chamber containing thesubstrate.
 19. A method for forming a dielectric layer on a substrate,comprising, in an atomic layer deposition process: forming a monolayerof organoaluminum on the substrate from an organoaluminum precursor gas;exposing the organoaluminum monolayer to oxygen and nitrogen gases toform a porous aluminum oxide monolayer; exposing the porous aluminumoxide monolayer to a silanol precursor gas to form a layer of silicondioxide about 100-300 angstroms thick thereon; and repeating theforegoing steps to form a laminate of alternating layers of the porousaluminum oxide monolayer and the about 100-300 Å thick layer of silicondioxide.
 20. The method of claim 19, further comprising, prior torepeating said steps, purging excess silanol precursor gas from achamber containing the substrate.
 21. A method for forming a dielectriclayer on a substrate, comprising, in an atomic layer deposition process,sequentially pulsing an organoaluminum catalyst precursor gas to deposita monolayer of the organoaluminum catalyst over the substrate; oxygenand nitrogen source gases to convert the organoaluminum catalystmonolayer into porous aluminum oxide; and a silanol precursor gas for acycle duration effective to form a layer of silicon dioxide about 100-30angstroms thick on the porous aluminum oxide monolayer.
 22. The methodof claim 21, further comprising, repeating said sequential pulsing ofsaid organoaluminum catalyst precursor gas, oxygen and nitrogen sourcegases, and the silanol precursor gas to form the dielectric layer.